1. Field of the Invention
This invention relates to apparatus for forming a gusset in a tubular plastic film, and more particularly it relates to gusset forming apparatus including folding panels that are disposed adjacent to the center plane of a film tube and are movable in the mutually opposite open areas defined by a pair of flattening plates to gusset the film and to permit adjustment of the depth of the gusset.
2. Description of the Prior Art
Folding elements are known for forming gussets in tubular films. Even if the folding elements of the prior art apparatus are centrally and symmetrically arranged with respect to the flattening plates and to the nip between the pinch rollers for taking off the flattened tubular film, the fold lines of the gussets may wander from the desired course. Such wandering may be caused by the nature and shape of the inflated tubular film, by the material which is processed and, if the tubular film is peripherally reciprocated as it is withdrawn, by the rotation of the flattening plates and of the pinch rollers about the axis of the tubular film.
It is an object of the invention to provide an apparatus which permits an inflated tubular film, even if it is subject to disturbing influences, to be gusseted in such a manner that the outer edges of the flattened tubular film will assume a predetermined, desired position, particularly a position in which they are aligned in cross-section.